Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of microorganisms.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. In addition to being unsightly and undesirable from an aesthetic standpoint, the mature calculus deposits are regarded by some as constant sources of mechanical irritation of the gingiva.
A wide variety of chemical and biological agents have been suggested in the art to retard calculus formation or to remove calculus after it is formed. Mechanical removal of this material periodically by the dentist is, of course, routine dental office procedure.
The chemical approach to calculus inhibition generally involves chelation of calcium ion and/or crystal growth inhibition which prevents the calculus from forming and/or breaks down mature calculus by removing calcium.
The prior art discloses a number of chelating agents for this purpose. British Pat. No. 490.384. Feb. 15, 1937, discloses oral compositions containing ethylenediaminetetraacetic acid, nitrilotriacetic acid and related compounds as anticalculus agents. U.S. Pat. No. 3,678,154. July 18, 1972 to Widder et al. discloses oral compositions containing certain polyphosphonates and fluoride. U.S. Pat. No. 3,737,533, June 5, 1973 to Francis discloses oral compositions containing certain carbonyl diphosphonates.
In addition to the above references, the prior art discloses dentifrices and mouthwashes containing soluble pyrophosphate salts which have been indicated for a variety of purposes. Included among such references are U.S. Pat. No. 2,941,926, June 21, 1960 to Salzmann et al. which discloses dental powders containing chlorophyll and pyrophosphate salts. U.S. Pat. Nos. 3,927,201 and 202, Dec. 16, 1975 to Baines et al. and Harvey et al., respectively, discloses toothpastes which utilize sparingly soluble pyrophosphates as abrasives. U.S. Pat. Nos. 4,244,931, Jan. 13, 1981 and U.S. Pat. No. 4,247,526, Jan. 27, 1981 to Jarvis et al. disclose pyrophosphate salts in dicalcium phosphate systems. Japanese Patent Application Disclosure No. 4945-1974 discloses soluble pyrophosphates in a variety of dentifrice systems. U.S. Pat. No. 4,333,551, Apr. 6, 1982 to Parran discloses tetraalkali metal salts in mouthwash compositions. U.S. Pat. No. 4,515,772, May 7, 1986 to Parran et al. discloses oral compositions containing soluble pyrophosphate salts as anticalculus agents. Finally Draus, Lesniewski and Miklos, Pyrophosphate and Hexametaphosphate Effects In Vitro Calculus Formation. Arch. Oral Biol., Vol. 15, pp. 893-896, (1970) disclose the in vitro effectiveness of soluble pyrophosphate salts against calculus.
A reference disclosing a variety of linear molecularly dehydrated polyphosphate salts as anticalculus agents in U.S. Pat. No. 4,627,977, Dec. 9, 1986 to Gaffar et al. Included among the salts is sodium tripolyphosphate (STPP). Another reference disclosing STPP is U.S. Pat. No. 4,923,684. May 8, 1990 to Ibrahim et al. This reference discloses STPP in a toothpaste having a pH of from about 8 to about 10 to reduce the hydrolysis of the material.
The present inventors have discovered that compositions containing STPP and other alkali metal or ammonium TPP materials, while stable at pH's in the range of 9 or higher, can suffer from causing irritation problems in the mouth.
The present inventors have also discovered that compositions containing STPP at pH's of 8 and below can be stabilized against hydrolysis by the inclusion of a soluble orthophosphate compound.
It is an object, therefore, of the present invention to provide stable tripolyphosphate compositions.
It is a further object to provide compositions which provide an anticalculus benefit and an anticaries benefit.
It is still a further object of the present invention to provide an effective method for treating calculus.
These and other objects will become more clear from the detailed description which follows.
All percentages and ratios used herein are by weight of the total composition unless otherwise specified and all measurements are made at 25.degree. C. in the composition unless otherwise specified.